Those "ads by google" is part of a program called Google Adsense. It's the opposite of Google's Adwords Advertising program.

You'll need to sign up for a free Adsense account, and you need to have some sort of blog or website where you can place those ads.

I recommend starting with Blogger.com. It's a free site that also happens to belong to Google.

Create a blog with a name related to the niche market you're trying to promote in.

Adsense ads are "contextual ads". This means they appear based on keywords that Google detects on your site.

There are advertisers like you and me that are, no kidding, bidding as high as $65 a click for certain keywords.

Google will split 68% of that with you. They just announced in May 2010 what the revenue share is. They never used to tell anybody.

However...

Getting people to click on those ads is not as easy as you think unless you plan ahead and plan well.

By the way, NEVER, EVER click on your own Adsense ads. Google will ban your account immediately. This is considered click fraud. You waste the advertiser's money without any intention to buy. Those people have no problem suing Google for carelessness.

First you need to write blog posts with your keywords in it, around 2 or three times. But you've got to choose keywords that get high traffic and low competition.

You also have to find out if people are actually clicking on ads for that keyword.

Google's keyword tool is not bad. It will give you generic information, but it won't tell you the strength of your competition.

What you need to do in order to get visibility on the search engine results is you want your blog post to end up on the first page of Google because nobody really searches past the first page.

When your useful content filled blog (don't make it sound like an advertisement) has the right high-traffic, low-competition keywords in it and you publish it to the web, in about 3 days to a week (sometimes less), your page will be indexed.

But your page could end up on Page 20 or Page 4. You don't know. Because it depends on the strength of the competition of all the pages for that same keyword on other people's sites that has already been indexed.

Google factors in over 200 criteria to determine how a page is ranked anywhere in Google's cyberspace. But the Biggest factor is what you call backlinks.

A backlink is just a link that goes from one site to another. But the links that make your pages rank are the kind that come from high-ranking authority sites that have a page rank (PR) of 4 and above, preferably, that is related to the topic or the niche market you're promoting in.